Doctors in California's state prisons sterilized about 150 female inmates without required state approval from 2006 to 2010.

Witnesses and some of the women themselves said coercion was involved, and the physicians targeted women they thought had the best chance of returning to prison or those who have multiple children.

One of the physicians involved defended the practice, saying he didn't pressure anyone and offered the service to poor women who had at least three caesarian sections, the report noted.

The women he sterilized refuted his claim, saying he kept talking about it more and more during their pregnancies. "He made me feel like a bad mother if I didn't do it," one woman said.

Another woman claimed the doctor tried to pressure her into having a tubal ligation while under sedation for a C-section, causing her to panic. She refused the procedure.

In 33 states, incarcerated women give birth in shackles, according to Jezebel, which was the case in California during the time of the coerced sterilizations. The state banned the use of shackles during prison births in 2012.

In response to the Center for Investigative Reporting story, three state legislators, Ted Lieu, Hannah Beth-Jackson and Noreen Evans, demanded the state's medical board investigate the physicians involved.

The letter to Sharon Levine, president of the Medical Board of California, read in part:

"Physicians are required to get actual consent – not a coerced agreement – before performing a surgical procedure on a patient, especially in the case of a tubal ligation, which can have life altering effects and is largely irreversible. The CIR story raises troubling allegations that doctors violated state law, disregarded ethical guidelines, and fell well below the standard of care."

The Sacramento Bee spoke out against the prison sterilizations in an editorial: "At best, physicians and prison officials displayed an appalling ignorance of the rules. At worst, they betrayed patients' trust – and ventured uncomfortably close to past abuses in which forced sterilization was used to stop criminals, the mentally ill and the poor from having more children."

The forced sterilizations continued until the 1970s in some states. Involving men and women, the laws targeted the disabled, minorities, the poor, prisoners, people deemed mentally unfit, sexually deviant and other socially disadvantaged groups.

According to Kaelber, American eugenics inspired Nazi Germany's forced sterilizations, which sterilized about 350,000 from the mid-1930s until the regime fell in 1945.

California topped the nation's compulsory sterilizations of its powerless citizens, accounting for one-third of the nation's forced sterilizations. Before 1964, more than 20,000 had gone under the knife.

California's law was repealed in 1979. Assemblyman Art Torres discovered the measure's existence after several Los Angeles residents of Mexican descent sued a local public hospital for giving them nonconsensual tubal ligations after their C-sections, according to Alexandra Minna Stern in the American Journal of Public Health. Mexican-Americans were disproportionately targeted by the state of California because of their traditionally large families, Kaelber noted.

Native Americans were also sterilized in large numbers in the 1970s, "which by some accounts led to sterilization rates of more than 25 percent among women of child-bearing age," Kaelber said.

She pointed out that the U.S. has largely ignored these human rights abuses.

"While Germany has taken important steps to commemorate the horrors of its past, including compulsory sterilization (however belatedly), the United States arguably has not when it comes to eugenics," she said.

"For some states, there still is a paucity of reliable studies that show how and where sterilizations occurred. Hospitals, asylums, and other places where sterilizations were performed have so far typically chosen not to document that aspect of their history," Kaelber added.